Farm Tech

In The Paddock
Seasonal sheep flock management tips October 2002

Managing the spring pasture flush

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Key points

• 50 – 70 per cent of the year's pasture growth normally occurs during spring/early summer.
• To maximise profit, as much of this pasture as possible should be converted into liveweight gain. To achieve this, the pasture should be of high quality.
• Pasture surpluses need to be managed so the build up of low quality dead material is minimised. If pasture has a lot of dead material in it, lambs may not gain any weight.
• The aim of grazing management should be to keep average cover from 1400 – 1800 kgDM/ha, or 4 – 6 cm, and to enhance clover growth.
• Surplus late-spring pasture can be conserved as hay or silage, topped, controlled with low rates of herbicide, or grazed with cattle or weaned ewes.

The most efficient way to manage the surge of growth in spring and early summer is to convert it into liveweight gain while it is green, leafy and growing in the paddock.

The aim of grazing management should be to keep average cover from 1400 – 1800 kgDM/ha, or 4 – 6 cm, and to enhance clover growth.

This can be a challenge. In most regions, 50 – 70 per cent of the year's pasture growth occurs in spring and summer.

If pasture mass is not controlled and reaches 3000 kg DM/ha, up to 50 per cent of it can die off and decay.

Lamb growth is the first priority for spring/summer feeding, while ewe liveweight gain is a close runner-up. Ewes in good condition will have good lambing percentages the following season.

Pasture is most efficiently converted to liveweight when animals are growing rapidly. This is because a smaller proportion of the feed consumed is used for maintenance.

Also, when lamb drafting weights are achieved earlier, there is less competition for feed with the ewes. This in turn leads to an overall reduction in the feed requirement of the sheep operation.

Feed quality has a major influence on the level of production achieved by ewes and lambs. On high quality growth (ME value 12) gains of 300 g/day are possible, while on lower quality material (ME value 9) lambs will lose weight.

The digestibility of new spring growth is close to 80 per cent, with an ME value over 12 MJ ME/kgDM. In summer, as leaf material ages and dead matter and seed stem material accumulates, feed quality drops steeply. This is clearly shown in the diagram.

Controlling pasture cover

In late lactation, pastures often grow faster than ewes and lambs can eat them.

The best way to manage this potential surplus is to graze it. Prolific ewes and their rapidly growing lambs do the job very well. Indeed, at high lambing percentages, surpluses may not occur at all.

But on most farms, this surplus needs to be anticipated and managed effectively. Otherwise, the accumulated growth will age and die. Pasture and animal growth rates will both suffer.

To enable grazing pressure to be maintained on the rest of the property, many farmers retire a proportion of the farm from grazing by ewes and lambs. Usually the closed-up area is cut for hay or silage.

When closing-up paddocks, care needs to be taken not to tighten the ewes and lambs up so much that production suffers. Remember, the aim is to keep covers in the 1400 – 1800 kgDM/ha range.

In some cases, very steep or rough paddocks are taken out of the grazing rotation altogether. This may not be the best course of action—research has shown it is better to leave smaller, more fertile paddocks ungrazed, as they are easier to clean up with stock later. They also recover better in terms of retaining desirable pasture species.

On hill country, where there is little suitable land for hay or silage making, cattle are often used to increase stocking rates. They can prepare the paddocks before the sheep graze them or can be rotated through the sheep mobs. Strategic electric fencing can be used to concentrate the cattle on rank areas.

Other ways to manage summer feed surpluses include topping to prevent grasses going to seed and the build-up of dead seed stem. Or herbicides like Roundup® can be applied at low rates to prevent grasses going to seed and to encourage clover growth.

Lambs grow faster on clover-dominant pastures (more than 30 per cent clover). Growth rates of weaned lambs can be 250 – 300 g/day on such swards, compared with 150 – 200 g/day on ryegrass-dominant swards.

Clovers grow at higher temperatures than ryegrasses and have a later growing season. Encouraging clovers into the sward will be rewarded with higher quality pastures and higher lamb growth rate during summer.

Set-stocking, especially with cattle, encourages clover dominance.

More information

In The Paddock, September 2001. Ewes need priority feeding after lambing.

In The Paddock, October 2001. Managing pasture for maximum feed quality.

In The Paddock, November 2001. Feeding weaned lambs for maximum growth rate.

In The Paddock, July 2002. Achieving target pasture covers in time for lambing.

In The Paddock, August 2002. Principles of pasture growth.

Your local farm consultant or veterinarian will also be able to help. Alternatively, contact your local Meat & Wool Innovation extension specialist: